Carried somehow, somewhither, for some reason, on these surging floods, were these travelers,[…]. Even such a boat as the Mount Vernon offered a total deck space so cramped as to leave secrecy or privacy well out of the question, even had the motley and democratic assemblage of passengers been disposed to accord either.

The dawn of the oil age was fairly recent. Although the stuff was used to waterproof boats in the Middle East 6,000 years ago, extracting it in earnest began only in 1859 after an oil strike in Pennsylvania. The first barrels of crude fetched $18 (around $450 at today’s prices).

There is no explicit limit, but the word boat usually refers to a relatively small watercraft, smaller than a ship but larger than a dinghy. It is also the normal designation for a submarine (however large), and also for lakers (ships used in the Great Lakes trade in North America).